The explosion took place in front of a restaurant on a highway in Isulan in Sultan Kudarat province.

An initial investigation was underway and there were no suspects or immediate claims of responsibility, police said.

The province is on the Philippines’ second-largest island, Mindanao, parts of which have been plagued by decades of Maoist and Islamist rebellions that have given rise to banditry and extremism. Mindanao remains under martial law until the end of the year.

According to initial reports, one person was killed, one critically injured and 34 others wounded, said provincial police chief, Noel Kinazo. Radio station DZRH reported multiple fatalities.

The incident comes a month after a bomb was detonated in a van that was stopped at a military checkpoint on the island of Basilan which killed 11 people, including four civilians.

Islamic State claimed responsibility, which the military disputes, suspecting that a local group was behind it, with the intended target civilians in an urban area.